We are actively working on a solution that will fully sandbox package installations for npm, yarn, poetry and others.
It's rolled up as part of our core CLI [1], but is totally open source [2]:
[1] https://github.com/phylum-dev/cli [2] https://github.com/phylum-dev/birdcage
Though I’m not sure of the solution really is / should be increased sandboxing.
The alternative may be a rethinking of the increasingly smaller packages. Maybe it’s better to have few large packages maintained by reputable organisations or personalities?
We really need a defense in depth approach here. Sandbox where it makes sense, perform analysis of code being published, consider author reputation, etc.
If you put code in the package itself, this would side step the "installation" sandbox. However we're also doing analysis of all packages introduced to the ecosystem to uncover things that are hiding in the packages themselves.
So you're right, we need a defense in depth approach here.